Utilization of heat of finely divided solids



Jan. 1, 1952 H. J. OGORZALY ETAL 2,531,041

UTILIZATION OF HEAT OF FINELY DIVIDED SOLIDS Filed Nov. 14, 1947 3 Sheets-Sheet l 82 BURNER VESSEL RAW SHALE TO PRODUCT HOPPER L80 4 RECOVERY RAW SHALE PREHEATER 92- 72 SPENT SHALE G 2 49 v, t t T 32 COOLER -5o FLUlDlZlNG A 76 8 SHALE 54 1 56 t 8 1 V 5a 96 COLD SPENT AIR INLET SHALE OUTLET 1 iNVENTORS HENRY J. OGORZALY AND WALTER A. REX

*9 WWW ATTORNEY Jan. 1, 1952 Filed Nov. 14, 1947 H. .I; OGORZALY rAL UTILIZATION OF HEAT 0F FINELY DIVIDED SOLIDS BURNER vEssEI A TO PRODUCT RECOVERY 94 as f RETORT l 92- 8 74 FLUIDIZING 1 STREAM INLET T0 BURNER VESSEL 9s 60 AIR INLET FIGJI.

5 sheets-Sheet 2 RAW SHALE HOPPER RAW SHALE PREHEATER SPENT SHALE (LQOLER 36 STEAM SPENT SHALE QUENCH COLD SPENT SHALE INVENTORS HENRY J. OGORZALY, AND WALTER A REX ATT OR NEY Jan. 1, 1952 H. J. OGORZALY EI'AL. 2,531,041

UTILIZATION OF HEAT 0F FINELY DIVIDED squns Filed NOV. 14, 1947 3 Sheets-Sheet :5

RAW SHALE TO PRODUCT HOPPER) 82 s 4 RECOVERY BURNER VESSEL RAW SHALE PREHEATER TUBES SPENT SHALE COOLING BED 32 66 I 5" SPENTSHALE f/ QUENCH COOL SPENT TO BURNER VESSEL 96 SHALE OUTLET AIR INLET INVENTORS HENRY -J. OGORZALY, AND WALTER A. REX

ATTORNEY Patented Jan. 1, 1952 UTILIZATION OF BS1551. OF FINELY DIVIDED LIDS- Henry J. Ogorzaly, Summit, and Walter A. Rex,

Westfleld, N. J., assignors to Standard Oil Development Company, a corporation of Delaware Application November 14, 1947, Serial No. 785,898

6 Claims. (Cl. 202-27) -The present invention relates to the utilization of the sensible heat of hot finely divided solids and, more particularly, to improved means for transferring the heat of finely divided solids which have undergone a high temperature treatment to fresh finely divided solids which are to be subjected to the same high temperature treatment.

The invention may be applied in all'processes which involve the treatment of finely divided solids at an elevated temperature to yield a finely divided solid product and which require preheating of the finely divided solids feed to the treating zone. Greatest advantages may be derived from the invention in connection with such processes of the type just specified as require a substantial cooling of the finely divided solids product recovered from the treating zone.

An outstanding example for such processes is the distillation of oil shale in a subdivided form to yield valuable volatile products and a subdivided solid carbonaceous shale residue. The distillation process is usually carried out at temperatures of the order of from 800 to 1000 F. Emcient operation requires preheating of the fresh shale to temperatures just below the temperature of beginning distillation, say to about 400 to 600 F. The spent solid carbonaceous shale residue, on the other hand, which is recovered substantially at distillation temperature must be cooled below its ignition temperature, that is below about 300 F; in order to avoid spontaneous ignition.

Analogous requirements have to-be met in various other. operations involving the treatment of subdivided solids at elevated temperatures such as the roasting and/or reduction of many types of ores and the like.

It is the principal object of the present invention to provide improved means for utilizing the sensible heat of subdivided solids having undergone a high temperature treatment, to precondition, i. e. to preheat and/or dry the subdivided solids feed to said high temperature treatment.

Other and more specific objects and advantages will beappa-rent from the more detailed description hereinafter in which reference will be made to the accompanying drawing.

In accordance with the present invention, a substantial portion of the sensible heat of subdivided solidssubjected to a high temperature treatment. in such amount as may be readily utilized at a high temperature level, is transferred to the fresh subdivided solids feed for said treatment at a desirably high temperature level, while the remainder of said sensible heat, which frequently may not be utilized at said desirably 2 high temperature level, is used to improve the emciency of the heat transfer from the relatively hot product solids to the relatively cool fresh feed solids.

More specifically, a substantial portion of the sensible heat of the hot solids recovered from the high temperature treatment is transferred to a fluid heat transfer medium, such as a vapor or gas which is then contacted with the fresh cold solids to preheat and/or dry the latter, while the remainder of the sensible heat of the hot solids is utilized to produce a fluidizing gas such as steam or other vapor from water or another vaporizable liquid. The fluidizing gas so produced serves to fluidlze the solids during their heat exchange with the heat exchange fluid so as to establish ideal heat transfer conditions during the heat exchange. In this manner, a substantial portion of the sensible heat of the hot solids may be utilized at a high temperature level to preheat and/or dry the solids feed while the portion of the sensible heat which normally can not be efficiently utilized for this purpose is usefully employed to improve heat transfer conditions.

Having set forth its objects and general nature, the invention will be best understood from the more specific description hereinafter wherein reference will be made to the accompanying drawing in which Figure I is a partly diagrammatical and partly schematic illustration of a system adapted to carry out one embodiment of the invention;

Figure 11 is a similar illustration of a suitable modification of the embodiment of the invention shown in Figure I; and

Figure III illustrates, in a similar manner, another embodiment of the invention.

Referring now to Figure I of the drawing, the system illustrated therein essentially comprises a vessel or reaction retort i0 and a heat transfer chamber 30, the functions and cooperation of which will be forthwith described using as an example the distillation of shale. It should be understood, however, that the invention may be applied to the heat treatment of other solid materials in a generally analogous manner.

Retort in may be of any conventional design suitable for the treatment of subdivided solids at high temperatures such as of the order of from 900 to 1100 F. or higher. For illustrative purposes, retort i0 is shown in the form of an enlarged vertical vessel in which a body of finely divided shale is maintained in the form of a dense, turbulent, pseudo-liquid mass fluidized by an upwardly flowing gas to form a well defined upper level LlO- The gases assisting in the distillation and fluidization of the shale, such as highly heated steam, product gas, and/or oxidizing gas such as air, oxygen or a mixture of such oxidizing gases, are introduced into the bottom portion of retort I through line [2. The bottom portion of retort I0 is provided with a horizontal perforated grid l4 through which the gases pass upwardly into the main portion of the retort.

The velocity of the gases passing through grid 14 is sufficient to prevent sifting or passing of the powder backwardly into the gas inlet l2. To this end the total area of the openings in grid l4 may be V4, or less, the total cross-sectional area of retort l0. After passing through grid H, the gases contact the finely divided shale undergoing distillation. The cross-sectional area of retort I0 is so designed that the velocity of the gases passing upwardly through retort i0 is such as to lift the particles of shale and form a relatively dense, turbulent, fluid mixture of gases and shale. Under properly controlled conditions, which may include superficial gas velocities within retort l0 of about 0.5 to 3 ft. per second for shale particle sizes falling within the broad range of about 5 to 5,000 microns, a mobile, turbulent, fluidized mass of shale is maintained above grid l4 having the general appearance of a violently boiling liquid. This fluidized state of the shale in retort l0 results in a substantially uniform temperature throughout the shale mass in all directions.

Volatile shale distillation products, fluidizing into a dense, turbulent, fluidizedbed of solids resembling a boiling liquid and having a well defined upper level L31. Heat-absorbing coils 34 of a heat transfer fluid circuit 31, 38 are immersed in the fluidized bed of hot spent shale and serve to extract heat from the spent shale. The dense fluidized nature of the mass of hot shale in section 3! permits a high heat transfer rate at the high temperature level of the spent shale, resulting in a rapid and highly efiicient heat conductance from this shale to the heat transfer medium.

The heat transfer fluid such as Dowtherm or the like heated in coils 34 substantially to the average temperature of the spent shale in section 34. of say about 500-700 F., passes upwardly through line 38 into coils 39 arranged in the upper shale preheating section 40 of chamber 30. Section 40 is provided with a perforated bottom plate 42 similar to grid 32 of section 31. Fresh cold shale is supplied from fresh shale hopper 44 through line 46 to section 40 wherein the bed of fresh shale is converted by the flow of vapors entering the bottom of section 40 from section II through grid 42 into a dense, turbulent, fluidized mass of solids forming an upper level L40 and having the excellent heat transfer characteristics described in connection with the fluidized spent shale mass in section 3|. The combined action of the heat transfer fluid in coils 39 and of the vapors passing through grid 42,

, which both enter section 40 at a temperature of gas and entrained spent shale fines are withdrawn overhead from level Lin and passed to a gas-solids separation system It which may comprise conventional centrifugal and/or electrical precipitators or filters. Volatile products substantially free of shale fines are withdrawn through line' i8 and passed to a conventional product recovery system (not shown). Separated spent shale fines may be returned to retort l0 through solids return lines I9 and 20.

The shale is maintained in retort [0 for a period substantially sufficient completely to distill of! its volatizable constituents. Residence times of about .5 to minutes, preferably about 1 to 10 minutes, are suitable for this purpose. A stream of fluidized, hot, solid, carbonaceous shale residue may be withdrawn from retort 10 through line 22 and passed substantially at the temperature of retort Hi to a middle portion 3| of chamber 30, as shown in the drawing. Line 22 is preferably connected to a lower portion of retort [0. A suitable aerating gas, such as steam, may be introduced into line 22 through line 24 to facilitate the flow of the fluidized shale residue through line 22 so as to utilize the pseudohydrostatic pressure of the fluidized shale above valve 26 in line 22 for conveying the shale from retort Hi to chamber 30'. The amount of gas introduced through line 24 is considerably less than the amount passing through line l2 and the density of the finely divided shale in line 22 is substantially greater than the density of the fluidized mass within retort Ill. The amount of spent shale passed through line 22 to chamber 30 roughly corresponds to the content of ash plus non-volatilizable carbonaceous constituents in the fresh shale supplied to retort i0 as will appear hereinafter.

Intermediate section 3| of chamber 30 is provided at a point below the point of spent shale discharge with a perforated grid 32 through which vapors formed as hereinafter described pass upwardly through section 3| at a rate adequate to convert the mass of spent shale above grid 32 about 500-700 F., rapidly heats the fresh shale in section 40 to an average temperature of about 350500 F. In order to permit proper fluidization of the fresh shale in section 40 in spite of the volume contraction of the fluidizing vapors resulting from the temperature drop of about l00-300 F. between sections 3| and 40, the diameter of section 40 is preferably somewhat smaller, for example by about smaller, than that of section 3|, as indicated in the drawing. The fresh preheated shale may be supplied by gravity flow through line 48 to an upper portion of retort [0, to undergo distillation as described above. Heat transfer fluid of reduced temperature returns through line 31 to coils 34, while cooled fluidization vapors may be withdrawn from level L40 through line H to the atmosphere. Either or both of lines 46 and 48 may have the form of aerated standpipes as indicated on the drawing in a manner which will be readily understood by those skilled in the art.

Returning now to section 3|, the finely divided spent shale, after having given off a substantial portion of its heat at a high temperature level to the heat transfer fluid and fluidization vapors and indirectly to the fresh shale, overflows through a downcemer or vertical conduit 49 and discharges into bottom section 50 of chamber 30, wherein the final cooling is accomplished and the fluidizing vapors are simultaneously generated.

Final cooling of the spent shale and generation of fluidization vapors are accomplished by injecting water through line 54 into the shale supplied to section 50 through conduit 49, while the shale is maintained above the vaporization point of the water, say at a temperature of about 250-350 F. The water may be discharged into the bottom of section 50 through a plurality of nozzles 58 or through a suitable cone distributor.

The water upon being injected into the relatively hot spent shale is vaporized and the vapors pass upwardly through the shale in section 50 at a velocity adjusted again to form a relatively dense fluid layer of solids therein having an upper. level Lee. The vapors after passing through section 66 continue upwardly through the grid 32 into section 3| to fluidize the shale therein while absorbing heat therefrom, and thence through grid 42 into section 40 to fluidize and preheat the fresh coarse shale as described above. In this manner, a substantial portion of the sensible heat of the spent shale is eiliciently utilized even at a relatively low temperature level for the preheating of the fresh shale, while the spent shale is simultaneously cooled below its spontaneous ignition temperature.

At the temperature conditions given herein by way of example and assuming a spent shale circulation through pipes 22 and 46 of about 0.70 to 0.85 lb. per lb. of fresh shale supplied through pipe 46, an amount of about 0.03 to 0.07 lb. of water supplied through line 46 per lb. of fresh shale to be preheated from about 60' F. to about 300-500 F. in section 40, is usually adequate for the dual purpose of spent shale cooling and proper shale fluidization in..zones 60, 3| and 40. The superficial velocity of the fluidization vapors in sections 3| and 60 is preferably in the range of 0.5-1.5 ft. per. sec. and in section 40 preferably in the range of about 1-4 ft. per sec. At these flow conditions, the amounts of solids carried overhead from levels Lso. Lu and L40 are so inconsequential relative to the amount of solids being withdrawn as not to interfere with an efilcient operation of the process even in the absence of gas-solids separators arranged between the various sections. However, gas-solids separation systems of the type indicated at i6 may be provided, if desired, in a manner obvious to those skilled in the art.

The relatively cool shale is finally withdrawn from the bottom of section 50, preferably by gravity flow, through line 58 provided with valve 60 for adjusting level Leo and controlling the rate of shale discharge.

From the foregoing it will be readily appreciated that the hot spent solids withdrawn from re-' tort l are subjected to a two-stage heat exchange in the course of which a substantial portion of the sensible heat is recovered and transferred to the fresh solids charge while the remainder of the sensible heat serves to improve the heat transfer rate between the solids by the generation of a fluidizing medium. Simultaneously, the hot spent material is cooled down to a desirable low temperature suitable for its discharge and storage.

The embodiment of the invention illustrated by Figure 11 of the drawing essentially comprises the same principal elements as shown in Figure I,

. like reference characters identifying like elements.

The cooperation between retort I0 and chamber 30, the operation of retort iii, the flow and fluidization of solids through and within the individual sections of chamber 30 as well as the temperature conditions in these individual sections are generally those outlined in connection with Figure I and need not be repeated here in detail. The system of Figure II, however, differs from that of Figure I in the means used for transferring the heat of the solids in section 3| to the solids in section 40.

8 indirectly to steam. The steam so heatedpass'es upwardly into section 40 wherein its heat content is given up by direct contact with the fresh solids charge In. accordance with the preferred modification of this embodiment of the invention, section 3| is provided with a steam coil 34 to which low pressure steam may be supplied through'line 31. The steam while flowing through coil 34 is rapidly heated to the average temperature of the fluidized solids in section 3|, say in a temperature of about 500-'700 F. The hot steam is withdrawn through valved pipe 36 which discharges preferably at a point closely below grid 42. In this manner, the steam highly heated in section 3| may be introduced through grid 42 into section 40 substantially at the temperature of section 3|. If desired, pipe 36 may be suitably heat-insulated to reduce heat losses by radiation. The steam discharged from pipe 36 cooperates with the hot fluidization vapors withdrawn overhead from level 1m to preheat and simultaneously fluidize the fresh solids charge above grid 42. The proper rate of steam supply through coil 34 and pipe to section mainly depends on the quantity of heat to be transferred from section 3| to section 40 and the relative temperature levels in the two zones. Assuming conditions similar to those specified in connection with Figure I, it may be stated that about 0.4 to 1.0 lb. of steam per lb. of 'raw shalev to be preheated from about 60 to about 350-500 F. is generally sufficient for the purposes of the invention.

The transfer of heat from the hot solids in section 3| to the fresh solids charge in section 40 may be further intensified in certain cases by contacting auxiliary steam directly with the fluidized solids in section 3| so as to augment the fluidization vapors rising from section upwardly through sections 3| and 50. This auxil- 'iary low pressure steam may be introduced through line 36 in addition to or in placeof the steam fed through line 31 and coil 34. The relative quantities of steam passed through lines 36 and 31, respectively, will mainly depend on the desired fluidization conditions in section 3|.

For example, when the density of the solids in section 3| is low or their particle size relatively small, say within the approximate range of 50 to 300 microns in the case of spent shale, substantially all of the auxiliary steam will be advantageously supplied through line 31 and coil 34 in order to prevent excessive entrainment of spent solids in the combined fluidization and heat exchange vapors. As the density of the solids increases or their particle size increases, the auxiliary steam supply may be shifted as a whole or in part to pipe 36.

It will also be understood that direct steam supply through line 36 to the partial or complete exclusion of coil 34 may be further favored by the arrangement of eflicient gas solids separation systems between sections 3| and 40, as mentioned in connection with Figure I. In the case of spent shale cooling as described, the amount of steam supplied through line 36 as a heat exchange medium in addition to the fluidization vapors rising from section 50 should be such as to establish at the conditions of zone 3| vapor velocities within the range of about 0.5 to, 3.0 ft.

per second. It will be readily appreciated by those skilled in the art that the system illustrated in Figure II ailords the same advantages of waste heat utilization at optimum temperaconnection with the example retort l may be operated in substantially the same manner and at substantially the same conditions as outlined in connection with Figure I. Spent shale may be withdrawn sub- ;stantially at the temperature of retort III of, say, about 900-1100 F. and passed through line 22 to intermediate section 3| of chamber 36 as described above. 'A dense, fluidized, turbulent mass of spent shale having an upper level L31 is formed above grid 32. Spent shale overflows through downcomer 49 into lower section 50 of chamber 36 wherein it is quenched with a vaporizable liquid such as water supplied through nozzles 56 to generate the upflowing vapors required for the fluidization of the solids in section 31. While the arrangement up to this point is similar to those of Figures I and II, diiferent means are employed for transferring the sensible heat of the hot spent shale in section 3| to the fresh cold solids supplied from hopper 44.

For this purpose, the fresh finely divided solid charge, such as raw shale of room temperature passes from hopper 46 by gravity flow downwardly through standpipe 46 into a buffer hopper 62 wherein the shale may remain for a time sufficient to reach a temperature of about 100- 150 F. in indirect heat exchange with hot fluidization vapors flowing overhead from level Lei.

The slightly preheated shale passes from hopper 62 into a plurality of vertical heat exchange pipes 64 imbedded in the hot fluidized shale mass in section 3|. On its downward path through tubes 64, the fresh shale abstracts heat from the hot spent shale by indirect heat transfer to reach a temperature of about 350500 F. by the time it leaves heat exchange tubes 64 downwardly. The shale preheated in this manner is collected in a second buffer hopper 66 arranged within the bottom section 50 of chamber 36. If desired, the solids within tubes 64 may be fluidized in order to improve their heat transfer coefficient and to reduce the temperature differential between the solids within and outside tubes 64 to a minimum. For this purpose, small amounts of any desired fluidizing gas may be injected into a lower portion of tubes 64 by way of taps 68. n A suitable fluidizing gas is available in the form of the fluidizing vapors vented through vent H, which may be wholly or in part returned through line 12 to taps 66. Another portion of thesev vapors may be branched off through line 14 and supplied through tap 16 to the bottom of hopper 66 to keep the solids therein 'in an aerated mobile state. In many cases this latter supply of vapors may be sufficient to fiuidize both hopper '66 and tubes 64.

The preheated shale collected in hopper 66 may be passed by gravity flow through pipe 48 into gas feed line l2 wherein it is picked up by the gases assisting in the distillation and fiuidization of the shale and conveyed through grid I4 into retort l0.

Instead of feeding the preheated shale through through line l2 to the bottom of retort In, it may be desirable to supply the fresh shale to an upper portion of retort l0, independently of the oxidizing gases flowing through line l2.

This may be accomplished by any conventional means such as mechanical conveyors or pneumatic means. In the latter case, the pseudo-hydrostatic pressure of the fluidized shale in the bottom o'fhopper 66 may be utilized to transport a shale column of lesser density, e. g. diluted with a small amount of an inert gas, such as steam, to an upper portion of retort III in a manner known per se in the art of fluid solids handling.

In the foregoing description, the specific manner of generating the heat required for the desired treatment in retort ID has merely been touched upon because this detail of the process has no direct bearing on the essence of the present invention. However, when the process of the invention is applied to the treatment of combustible solids, such as the distillation or gasification of carbonaceous materials, it may be readily and advantageously adapted to most of the conventional methods of heat supply.

For example, when it is desired to supply the heat required in retort H) in the form of sensible heat of preheated process gases and preheated solids charge, it is sufiicient to preheat an inert gas such as steam supplied through line "to a suitable level. In the case of shale distillation, a steam preheating temperature of about 1300"- 1600 F. will be generally suflicient assuming an amount of steam of about 0.5 to 1.3 lbs. per lb. of shale, which corresponds roughly to that required for fluidization in retort Ill. The heat required for preheating this steam may be generated by burning the shale withdrawn through line 58.

If desired, heat may be generated within retort [0 by supplying an oxidizing gas such as air, oxygen or oxygen diluted with air through line 12 to support a limited combustion of combustible shale constituents in retort Ill. The amount of oxygen required for this purpose depends, of course, on the preheating temperature of the gas supplied through line I2 and on the preheat of the fresh shale. Assuming a preheating temperature of the gas of about 200-300 F. anda shale preheating temperature of about 350-500 F. an amount of oxygen of about 0.0013 to 0.005

upwardly to combustion chamber mol per lb. of fresh shale to be treated is generally sufiicient to maintain the solids within retort ID at a temperature of about 900-1100 F.

These two methods of heat supply to retort I may be employed in combination with the operation of the systems of Figures I to III substantially as heretofore described.

A third method of heat supply adaptable to the purposes of the invention utilizes the sensible heat of the solid combustion residue of spent shale heated by combustion of combustible constituents of spent shale in a separate combustion zone and returned substantially uncooled to reaction retort ill in amounts suflicient to supply the heat required therein. 1

When it is desiredto employ this third method of heat supply, spent shale is withdrawn from retort l6 through a bottom drawoff pipe 10 which may be aerated and/or stripped by means of a suitable gas such as steam, flue gas, product gas, etc. supplied in small amounts through one'or more taps 13. The spent shale is suspendedin line 14 in an oxidizinggas such as air and/or oxygen to form a dilute suspension which flows under the combined air pressure on line 14 and pseudo-hydrostatic pressure of the fluidized spent shale mass on the control valve I6 of pipe 16, 60. The superficial velocity of the dilute shale suspension is so controlled that a dense turbulent mass of fluidized shale is formed above grid 18 of chainber 80, having a well defined upper level Lao- This may be accomplished by maintaining superficial gas velocities of about 0.5 to 1.5 ft. per second in chamber 80. The amount of oxygen made available in chamber 80 should be suflicient to support combustion of combustible shale constituents to an extent affording a temperature rise of the spent shale by about 100-300 F. to a temperature of about 900-1300 F. About 0.05 to.

0.20 lb. of, oxygen in the form of air per lb. of shale supplied to chamber 80 is normally suflicient for this purpose under the same conditions of preheat and retorting temperature as stated for the single vessel case.

Flue gases may be withdrawn from level Lao through a conventional gas-solids separation system such as cyclone 02. Separated solids may be returned to chamber 80 through pipe 84 while hot-flue gases now substantially free of entrained solids leave through line 86 to be used in the system for fiuidization, stripping steam production and/or preheating purposes, or to be vented, as desired.

Hot solid shale combustion residue may be withdrawn through one or more bottom drawoff pipes 88 and returned through valved lines 90 and/or 92 to the top or bottom of retort 10, substantially at the temperature of chamber 80, in order to supply to retort 10 the heat required therein as sensible heat of hot combustion residue. Depending on the temperature differential between chamber 80 and retort l0, shale circulation rates of about -15 lbs. per lb. of fresh shale charged to retort In ata preheat temperature of about 350-500 F. are generally suitable for this purpose.

The cooling down of spent shale and the utilization of its sensible heat may be accomplished in chamber 30 substantially as described before. However, in accordance with a preferred embodiment of the invention, the higher temperature level of the shale combustion residue withdrawn from chamber 80 may be utilized for heat exchange in chamber 30. For this purpose, a portion of the shale withdrawn through one or more of lines 88 may be passed through valved line 94 to chamber 30 to be further treated as described above. As a result of the higher temperature level at which the shale residue in line 04 is available, a higher preheat temperature of the entering shale feed can be obtained than is the case when withdrawing the spent shale from retort I0.

The cooled spent shale withdrawn through line 58 from chamber 30 will usually contain considerable amounts of combustible constituents of the order of about by weight of carbon.

This residue may be at least in part returned through line 95 via line 14 to combustion chamber 80 to increase the amount of heat transferred to the fresh shale feed in chamber 40.

This expedient may be especially desirable in the event that the fresh shale feed contains considerable quantities of surface moisture in the range of 2 to 10% by weight. In this case, chamber 40 will be acting as a combination preheater and dryer and the preheat temperature of the feed entering retort 10 through line 48 will depend on the amount of water on the fresh shale,

the temperature levels in chamber 80 and retort ll, and on the amount of recirculation through line 96.

It will be understood by those skilled in the art that many suitable combinations of the various methods disclosed above for heat generation.

solids cooling and waste heat utilization maybe employed as desired.

The present invention will be further illustrated by the following specific example which applies to retorting of oil shale in a single vessel with heat for the process being generated by supplying air to the retort and burning some of the combustible shale constituents, the preconditioning of the fresh shale being carried out in the manner illustrated by Figure I.

Example Feed -Co1orado type oil shale (ground to pass through M; in. screen) Shale assay-40 gal. of oil per ton Feed rate (through line 46,

per hour 10,000 Fresh feed temperature,

Preheated feed temperature (to retort l0 through line Spent shale to chamber 30 (through line 22):

Rate, per hour 8210 Temperature, F 1020 Spent shale discharge (through line 58) Rate, per hour 8000 Temperature, F 300 Quench w a t e r (supplied through line 54) Rate, gal. per hour 59 Temperature, F 60 Chamber Chamber Chamber Diameter, in 24 24 i5. 5 Bed Temperature, F 300 560 400 Superficial Vapor Velocity,

ft. persec 0.9 1.4 3.0 Heat Transfer Surface Required, sq. ft 125 Vapors out through line H:

Rate. SCFM 172 Temperature, F. 390 Pressure, p. s. i. g 2

While the foregoing description and exemplary operations have served to illustrate specific applications and results of the invention, other modifications obvious to those skilled in the art are within the scope of our invention. Only such limitations should be imposed on the invention as are indicated in the appended claims.

We claim:

1. A method of preconditioning subdivided solids subjected to a high temperature treatment in a high temperature treating zone which comprises withdrawing a stream of hot subdivided into a separate heat exchange zone. passing fluidizing vapors upwardly through said heat exchange zone at a rate adjusted to maintain the solids therein in a dense, turbulent, fluidized state, maintaining a bed of subdivided fresh solids to be preconditioned in a heating zone, passing a gasiform medium upwardly through said bed at a, rate adapted to maintain said bed in a dense, turbulent, fluidized state, transferring a portion of the sensible heat of the solids from said heat exchange zone to said bed to supply heat to the solids therein by flrst transferring heat from said solids to a heat transfer fluid medium and thereafter bringing said heat transfer medium into indirect heat exchange relationship with the said bed if subdivided fresh solids. passing preconditioned subdivided solids from said bed to said treating zone, passing subdivided hot solids of reduced temperature from said heat exchange zone to a cooling zone, injecting a vaporizable liquid into said cooling zone while the solids in said cooling zone are above the vaporization temperature of said liquid, whereby said solids are further cooled and the liquid is vaporized to produce said fluidizing vapors, and withdrawing cooled solids from said cooling zone.

2. The method of claim 1 wherein said fluidizing vapors are used as said gasiform medium.

3. The method of claim 1 in which said heat transfer medium is steam.

4. The method of claim 1 in which the heat transfer from said heat transfer fluid medium to said bed is direct.

12 5. The method of claim 1 in which said imporizable material is water. 6. The process of claim 1 in which another portion of the sensible heat of said hot solids is transferred within said exchange mne through a heat transfer surface to said fresh solids.

The following references are of record in the file of this patent:

UNITED STATES ra'ran'rs Number Name Date 1,836,301 Bechthold Dec. 15, 1931 2,276,343 Ryerson et al Mar. 17, 1942 2,371,819 Hartley Mar. 20, 1945 2,399,450 Ramseyer Apr. 30, 1946 2,409,707 Roetheli Oct. 22, 1946 2,420,542 Jahnig May 13, 1947 2,431,462 Campbell et a1 Nov. 25, 1947 2,441,594 Ramseyer May 18, 1948 2,506,317 Rex May 2, 1950 FOREIGN PATENTS Number Country Date 286,404 Great Britain Mar. 8, 1928 484,050 Great Britain Apr. 29, 1938 586,391 Great Britain Mar. 18, 1947 586,992 Great Britain Apr. 10, 1947 

1. A METHOD OF PRECONDITIONING SUBDIVIDED SOLIDS SUBJECTED TO A HIGH TEMPERATURE TREATMENT IN A HIGH TEMPERATURE TREATING ZONE WHICH COMPRISES WITHDRAWING A STREAM OF HOT SUBDIVIDED SOLIDS FROM SAID TREATING ZONE, PASSING SAID STREAM INTO A SEPARATE HEAT EXCHANGE ZONE, PASSING FLUIDIZING VAPORS UPWARDLY THROUGH SAID HEAT EXCHANGE ZONE AT A RATE ADJUSTED TO MAINTAIN THE SOLIDS THEREIN IN A DENSE, TURBULENT, FLUIDIZED STATE, MAINTAINING A BED OF SUBDIVIDED FRESH SOLIDS TO BE PRECONDITIONED IN A HEATING ZONE, PASSING A GASIFORM MEDIUM UPWARDLY THROUGH SAID BED AT A RATE ADAPTED TO MAINTAIN SAID BED IN A DENSE, TURBULENE, FLUIDIZED STATE, TRANSFERRING A PORTION OF THE SENSIBLE HEAT OF THE SOLIDS FROM SAID HEAT EXCHANGE ZONE TO SAID BED TO SUPPLY HEAT TO THE SOLIDS THEREIN BY FIRST TRANSFERRING HEAT FROM SAID SOLIDS TO A HEAT TRANSFER FLUID MEDIUM AND THEREAFTER BRINGING SAID HEAT TRANSFER MEDIUM INTO INDIRECT HEAT EXCHANGE RELATIONSHIP WITH THE SAID BED IF SUBDIVIDED FRESH SOLIDS, PASSING PRECONDITIONED SUBDIVIDED SOLIDS FROM SAID BED TO SAID TREATING ZONE, PASSING SUBDIVIDED HOT SOLIDS OF REDUCED TEMPERATURE FROM SAID HEAT EXCHANGE ZONE TO A COOLING ZONE, INJECTING A VAPORIZABLE LIQUID INTO SAID COOLING ZONE WHILE THE SOLIDS IN SAID COOLING ZONE ARE ABOVE THE VAPORIZATION TEMPERATURE OF SAID LIQUID, WHEREBY SAID SOLIDS ARE FURTHER COOLED AND THE LIQUID IS VAPORIZED TO PRODUCE SAID FLUIDIZING VAPORS, AND WITHDRAWING COOLED SOLIDS FROM SAID COOLING ZONE. 